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Where would the location for an after market temp sensor be on the cylinder head? I want the original wiring and sensor to remain on the intake manifold but also want to run an aftermarket gauge and put the sensor on the cylinder head. Anyone have a picture? Thanks!
 

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Where would the location for an after market temp sensor be on the cylinder head? I want the original wiring and sensor to remain on the intake manifold but also want to run an aftermarket gauge and put the sensor on the cylinder head. Anyone have a picture? Thanks!
Note that I only have one port on the intake
 

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Note that I only have one port on the intake
I don't think you will find anything on your heads if early. You will have the factory one on the water crossover on the intake. I am not sure when they began using the temp sensor in the side of the head, maybe 1972-73?

The later heads did use a temp gauge on the side of the head itself. I enclosed an Ebay pic of a 1973 SD head and you can clearly see the cast/tapped hole on the side that gets the H2O temp sensor.

However, if I were being creative and wanted a sensor on the head, look at the second pic. This is a typical Pontiac head having no provisions for a temp sensor. You are looking at the hole at the end of the head, one on each end. A freeze/welch steel plug goes there as that is where water is found behind that plug. If me, I just might purchase the correct sized steel freeze plug, and an H2O temp kit like Autometer, and have the brass bung that comes with the kit brazed to the plug by drilling it the correct size to insert the bung and then have a reputable shop braze it up flush with the back side of the plug so it does not interfere with the cylinder casting. Gently knock the steel plug into the head and then simply insert the temp probe and wire up.

When you install the plug, do not use any sealant as the plug needs to ground to the block for the temp gauge to work. The probe uses a pipe plug type threads which are self sealing as they tighten up - but don't over tighten. Same goes for your manifold gauge.

The problem may be getting to the freeze plug in the head. If the head were off, less issues. Not sure how much clearance you have at the back of the block and firewall. But, you might be able to fit it into the front of the head and this would also be easier to knock out and re-install.

I don't know of any other way unless you are willing to drill a hole in the side of the head and have a shop braze/tig weld a bung into that hole for the temp sensor.

1973 SD Head.JPG
Pontiac Head, freeze plug end.JPG
 

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I wonder if you can use the heater hose connector and on the right bank at the back and get a T-fitting or fab a bung back there
 
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